Gas Tank Options for 1970 GS 455

I am restoring a 1970 GS 455 that was a mess of other parts from other years. I noticed this when I took it all apart. My question is that the car needs a new gas tank. I see that there are 1 vent and 3 vent options. How do I know which is correct for my car? I cannot tell from the old tank as it was already out of the car when I bought it, and I do not even know if it was the correct tank.
Thanks

Hugger I looked at the spectra premium tanks. One question. They have 1 or 2 vents for the tanks without EEC. I am not sure the tank I took out is the original tank so how do I know if I need 1 or 2 vents?